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Question

Describe how the OFB mode can be attacked if the IV is not different for each execution of the encryption operation.

Answer

OFB (Output Feedback) mode encryption is a method of encryption that requires a unique initialization vector (IV) for every encryption operation. If the same IV is used for multiple encryption operations, the OFB mode can be vulnerable to attacks that allow an attacker to decrypt the plaintext without knowing the key. To better understand OFB mode encryption, it is important to note that it is similar to the CBC mode of encryption. However, instead of using the previous ciphertext block as input, OFB mode generates a keystream by using the previous ciphertext output as input to the encryption algorithm. This keystream is then used for each plaintext block by encrypting the initialization vector with the encryption algorithm to generate the keystream. However, if an attacker encrypts the plaintext with the same key and IV as the original message, and then XORs the ciphertext with the ciphertext of the message they want to decrypt, the generated keystream will be the same. This allows the attacker to recover the plaintext without knowing the encryption key. Thus, to prevent such attacks, it is important that the IV for each execution of the encryption operation is unique. If you want to learn more about OFB mode encryption, you can visit brainly.com/question/25265909 #SPJ11.